Filter element and filter device having replaceable filters

ABSTRACT

Providing a filter device with various functions, such as remarkable improvement of the throughput of the downstream filter, ion-removing property of the upstream filter. A filter element comprises an upstream filter and a downstream filter made of the same or different material and installed into one housing or container, wherein said downstream filter is fixed to said housing, said upstream filter is fixed to said downstream filter, both filters are concentrically arranged to each other, and when the downstream filter is not contaminated, only the upstream filter can be replaced with fresh one.

BACKGROUND OF THE INVENTION

The present invention relates to a filter cartridge which is suitablefor filtering liquid and gas. More particularly, the present inventionrelates to a filter cartridge for filtering a liquid agent containinglarge amounts of various foreign matters, such as an amine-type organicrelease agent used on a substrate for electronic parts (e.g. asemiconductor wafer and a glass substrate for a liquid crystal device);a pigment-dispersion photoresist for a glass substrate of a liquidcrystal device; a slurry for a chemical and mechanical abrasion device;and other liquids used in general industry.

Two different and specific basic cartridges generally used for filteringgas and liquid are a depth filter (representatively a roll type filter)and a membrane filter (usually a pleated filter). Today, roll type depthfilters and membrane filters each encased in a separate housing are usedin tandem to attain a desired purification level. In Japanese PatentApplication Kokai No. 7-213814, a filter cartridge is proposed that hasa filter body comprising: a depth filter containing non-woven fiber massin the form of either roll or seamless fiber cylinder; and a pleatedscreen filter or a surface filter that can be encased in the samehousing with the depth filter. However, there are still demands forcombinations of filters that can attain specific properties, such asincreasing throughput and removing metal ions. By separately providingfilters each as a unit that can be combined to each other, productioncost can also be reduced.

FIGS. 1 and 2 show a conventional filter cartridge disclosed in JapanesePatent Application Kokai No. 7-213814. A cartridge 10 has a depth filter16 having an exposed outer surface 12, in the form of roll or seamlessfiber cylinder; a pleated surface filter or screen filter 18concentrically arranged in within the depth filter; a core 20 supportingthe inner surface of the surface filter 18 as well as having a number ofholes 23 as fluid passages; and a fluid outlet 14 for withdrawing afiltrate fluid (liquid or gas) from the core 20. The top end of thedepth filter 16 and that of the surface filter 18 are sealed. The topend of the filter cartridge 10 is completely sealed with a cap 19. Uponits use, the filter cartridge 10 is inserted into a housing 21 of afilter device, and liquid-tightly fixed to the wall of the housing via athread means and/or an O-ring provided around the fluid outlet 14.

A fluid (liquid or gas) to be purified is introduced between the housing21 and the cartridge 10, and the fluid passes from the outer surface 12towards the inside of the depth filter 16, and then through the surfacefilter 18. The purified fluid flows out to the central passage throughthe holes 23 of the core 20, and is withdrawn as a filtrate from thefluid outlet 14.

In the above-mentioned case in which two different filters are used, thefilter located upstream has relatively large pore diameter, while thefilter located downstream has relatively small pore diameter, in orderto increase the level of purification and to elongate the life of thefilter.

However, the above-mentioned two filters are integrally formed to be asingle filter element, and have disadvantages in that various possiblefilter combinations should be prepared that satisfy various purposes. Inaddition, the upstream filter is contaminated faster as compared withthe downstream filter, and thus even when the downstream filter is notcontaminated, the filter element cannot be used anymore, because of theshorter life of the upstream filter.

Therefore, the object of the present invention is to provide a filtercartridge comprising an upstream filter unit and a downstream filterunit, wherein both units can be combined to each other so that theupstream filter locates between the downstream filter and the housing toform a cartridge and the combination can be properly selected dependingon the purpose such as the removal of metal ions and can elongate thefilter life.

The present invention provides a filter element comprising a combinationof an upstream filter and a downstream filter, wherein the upstreamfilter is replaceable. As the result, the life of the downstream filteris elongated while attaining the required purified level, and inaddition, smaller number of filters is required in order to obtain thesame amount of filtrate as that in the case of the conventional filter.

The present invention also provides a filter element comprising anupstream filter and a downstream filter, each of which is properlyselected depending on the specific purposes, from the stock of variousfilters expected to be used in various applications. The upstream filtershould be replaceable, although it may be integrally formed as a part ofa disposable filter device, if necessary.

Specifically stated, the preset invention provides a filter elementcomprising an upstream filter and a downstream filter, wherein saiddownstream filter has a means for fixing to a housing, and said upstreamfilter is fixable to said downstream filter fixed to said housing; and afilter device containing said filter element fixed to the housing.

In one embodiment, the downstream filter has a first thread part, andthe housing has a second thread part which engages with the first threadpart.

In another embodiment, the downstream filter is integrally formed withthe housing.

In still another embodiment, the upstream filter is fixed to thedownstream filter via fitting.

Preferably, the upstream filter and the downstream filter are in theform of cylinder and so arranged that one nests in the other.

The upstream and downstream filters may have the same or differentfilter membrane selected from the group consisting of a pleated type,roll type or seamless fiber cylinder type depth filter containingnonwoven fiber mass; and a porous foam, hollow fiber or pleated membranefilter. A roll type filter may comprise various kinds of filter bodiesrolled together, and the roll type filter may also have a densitygradient.

The upstream filter may be a member selected from a set of filters,which set is different from a set from which a member is selected as adownstream filter.

The present invention also provides a filter device containing theabove-mentioned filter element

The upstream filter comprises, in the order from inside, a porous innersupport cylinder made of resin (core), and a filter body in the form ofsheet rolled around the core. If necessary, the upstream filter furthercomprises an outer support cylinder made of resin (sleeve) oralternatively a resin net, which surrounds the filter body. The top edgeand the bottom edge of the upstream filter are sealed with resin caps.

On the other hand, the downstream filter comprises, in the order frominside, a porous inner support cylinder (core), a filter bodysurrounding the core, and a porous outer support cylinder (sleeve) oralternatively a net, which supports the outer surface of the filterbody. The top edge and the bottom edge of the downstream filter aresealed with resin caps.

The combination of filters that comprises the filter body can beproperly selected depending on the purpose. The upstream filter has afilter body comprising a pleated type, roll type or seamless fibercylinder type depth filter containing non-woven fiber mass; and a porousfoam, hollow fiber or pleated membrane filter. The upstream filterlocates upstream the downstream filter in the housing, and it may not bemechanically combined with a downstream cartridge, although it ispreferred that both ends of the upstream filter be sealed with capshaving the structure which can be mechanically and liquid-tightlycombined with the downstream cartridge.

The downstream filter is a filter cartridge having a filter bodycomprising a pleated type, roll type or seamless fiber cylinder typedepth filter containing non-woven fiber mass; and a porous foam, hollowfiber or pleated membrane filter. One end of the downstream filter issealed with a cap, while the other end is sealed with a cap having afluid inlet or a fluid outlet. Each of the caps may be combined with theupstream filter via a twist-lock, an O-ring, and/or a thread. However,it may not necessarily be combined.

The materials for the filter body used for the upstream and downstreamfilters can be selected from those known in the art. Examples include PP(polypropylene), PTFE (polytetrafluoroethylene), UHMWPE (ultra-highmolecular weight polyethylene), PE (polyethylene), HDPE (high-densitypolyethylene), PES (polyether sulfone), nylon, polyester, PVDF(polyvinylidene fluoride), cellulose and SUS (stainless steel). Theinside and outside support cylinders of the upstream and downstreamfilters are made of rigid resin. When a net is used instead of thesupport cylinder, it can be made of the same material. The top andbottom caps may be in the form of ring or disk, depending on theposition at which they are used. They are fused by heat with the top orbottom edge of the laminated structure composed of the inner and outercylinders (or parts of the net) and the filter body. The material forthe caps is also selected from those known in the art.

EXAMPLE

The present invention-will be explained in detail in the following. Theterm “filter element” means the combination of an upstream filter and adownstream filter; the term “filter device” means a device in which afilter element is installed into a housing to form a usable device, theterm “upstream” means the relative position with respect to the gas orliquid flow (feed) to be purified. As will be described below, a part ofthe feed can be led directly into the downstream filter, depending onthe required cleanliness for the purpose.

Example 1

FIGS. 3-6 illustrate the filter element and the filter device accordingto Example 1 of the present invention. In the descriptions of thefigures, the terms “top” and “bottom” are used for the sake ofconvenience, and the axis line can be set to an arbitrary direction,such as the horizontal direction.

FIG. 3 shows a filter device 32 of the present invention in which afilter element 30 (see FIG. 6) of the present invention is installed.FIG. 4 shows a perspective view of an upstream filter 34, FIG. 5 shows aperspective view of an downstream filter 36, and FIG. 6 shows a filterelement in which the upstream filter 34 is partially inserted into thedownstream filter 36.

Referring to FIGS. 3 and 4, the upstream filter 34 has a filter body 38comprising a pleated type, roll type or seamless fiber cylinder typedepth filter containing nonwoven fiber mass; and a porous foam, hollowfiber or pleated membrane filter. All of these filter body types areknown in the art, and the description can be found, for example, in theabove-mentioned references. The upstream filter 34 is located upstreamof the downstream filter in the housing, and it may not beliquid-tightly combined with the downstream filter (i.e. by passing mayoccur which allows a small amount of flow), or if higher purification isrequired, it can be liquid-tightly combined with the downstream filter36 (i.e. there is no bypass to the downstream filter). The figuresillustrate the former, and the top end of the filter body 38 is seatedwith an annular cap 44 made of resin, and the bottom end is sealed withan annular cap 42 made of resin. The inner surface of the cap 42 has twoprojections 46 at diametrically opposite positions for fixing theupstream filter 34 to the downstream filter 36. If the bypass of thefeed to the downstream filter 36 is required to be blocked, the top andbottom ends of the caps 42 and 44 are sealed using O-rings.

Along the inside and/or the outside of the filter body 38 in the form ofcylinder, porous support cylinder or cylinders made of rigid resin canbe placed, and the top and the bottom ends can be integrally combined tothe caps 42 and 44, respectively. The figures contain a thin supportcylinder 43 located inside the upstream filter.

Referring to FIGS. 3 and 5, the downstream filter 36 is a filtercartridge having a filter body 48 comprising a pleated type, roll typeor seamless fiber cylinder type depth filter containing non-woven fibermass; and a porous foam, hollow fiber or pleated membrane filter. Thetop end thereof is sealed with an annular cap 52, and the bottom end issealed with a cap 50. Each of the caps may be combined with the upstreamfilter by means of a twist-lock, an O-ring, and/or a thread. However,depending on the required degree of purification, the filters may not bemechanically combined together and the upstream filter 34 may merelycover the downstream filter 36. Along at least the inner side of thefilter body 48 among the inner side and the outer side, rigid supportcylinder(s) having a number of circulatory holes 56 is provided. In thisembodiment, along both surfaces of the filter body 48, the rigid outersupport cylinder 54 and the rigid inner support cylinder 62 areprovided, and the top and bottom ends of the cylinders are integrallycombined to the caps 52 and 50, respectively On the cap 52, a filtrateoutlet 60 is formed having an O-ring for air-tightly or liquid-tightlyfixing the downstream filter to the housing 70 (FIG. 3). The outlet isconnected to the inside of the inner support cylinder 62.

The circumference of the cap 50 has two twist-lock grooves 58, each ofwhich accommodates the projection 46 of the upstream filter 34 Theintroduction part of each of the twist-lock grooves has a wide openingwhich accepts the projection 46 in the direction of the axis, and alocking groove 64 connected to the opening is formed, which locks theprojection 46 when the upstream filter is rotated.

In FIG. 6, the inner downstream filter 36 is in the middle of theinsertion into the outer upstream filter 34. These two filtersconstitute a filter element 30. They are installed into thepredetermined position, and the projections 46 of the upstream filter 34are inserted into the twist-lock grooves 58 of the downstream filter 36,and the upstream filter 34 is rotated, thereby engaging the projections46 with the locking grooves 64. FIG. 3 shows a condition in which bothfilters are combined at the determined position Except the initialinstallation, the upstream filter 34 and the downstream filter 36 arereplaced by the fresh ones at the work site of filtration, and theupstream filter 34 is likely to be replaced more frequently as comparedwith the downstream filter 36.

FIGS. 7 and 8 illustrate one embodiment of the upstream filter 34 andthe downstream filter 36. In this embodiment, the upstream filter 34comprises, in the order from the inside, an inner support cylinder 43having pores 45 and a roll type filter body 38 having fine pores, rolledaround the inner support cylinder 43. The downstream filter 36comprises, in the order from the inside, an inner support cylinder 62having holes 56, a pleated type filter body 48 surrounding the innersupport cylinder 62, and an outer support cylinder 54 having pores 55,supporting the outer surface of the pleated filter body 48.

Various constructions of filter bodies can be properly selected,depending on the purpose.

As shown in FIG. 3, the housing 70 has a housing bowl 71 wherein the topend thereof is opened and the bottom end thereof is closed except adrain outlet 80. The top end of the housing can be air-tightly orliquid-tightly engaged to a round wall of a housing head 74 via anO-ring. The outer surface of the round wall of the housing head 74 hasan external thread, to which an internal thread of a fastening ring 72is engaged. When the fastening ring is loosened and the housing bowl 71is removed, the upstream filter 34 and the downstream filter 36 becomeaccessible for replacing by fresh ones.

Referring to FIG. 3, the feed flows from the inlet 76 of the housinghead 74 to the space between the upstream filter 34 and the housing bowl71, and then passes through the filter body 38. The unfiltered portionof the feed flows to the bottom of the housing bowl 71 and is dischargedfrom the drain outlet 80 as a drain flow. In this case, a portion-of thefeed may be bypassed and flows directly around the downstream filter 34,but depending on the purpose, this is allowable. If necessary, O-ringscan be placed between the annular caps 44 and 52, and between theannular caps 42 and 50, in order to prevent the formation of bypass, asmentioned above. The semi-filtrate that has been passed through thefilter body 38 is then passed through the filter body 48 of thedownstream filter 36 and further purified. The filtrate flows into theinner porous support cylinder 62, and exits from the filtrate outlet 78of the housing head 74. Clogging of the downstream filter 34 is notlikely to occur, while clogging of the upstream filter 36 occurs easily.Therefore, the flow rate of the filtrate is measured while watchingclogging of the upstream filter 34, and when the upstream filter 34 isconsidered to have been clogged, the flow is paused and the housing bowl71 is removed to replace the upstream filter with fresh one. In order tofacilitate the replacement of the filter, the housing 70 and the housinghead 74 are engaged together via an O-ring, and the internal thread ofthe fastening ring 72 is screwed into the external thread of the housinghead 74, thereby allowing the opposite end of the fastening ring to urgethe housing against the edge of the housing head 74.

Experiments were carried out using the filter element and the filterdevice of this embodiment. As a filter body of the upstream filter, afive-layered roll filter obtained by rolling up a non-woven sheet madeof PP (polypropylene), having a film thickness of 380 μm, and weight of110 g/m² and the air-permeability of 0.36 sec was used, and as thefilter body of the downstream filter, Microgard Plus (10 inch, the porediameter of 0.05 μm, manufactured by Mykrolis Corporation) in which amembrane made of 0.05 μm UHMWPE (ultra-high molecular weightpolyethylene) was used. As a testing fluid, water containing 500 ppm ofAC fine test dust was used. The filtration was conducted at the pressuredifference of 55 kPa. The lowering of the filtration performance of theupstream filter due to the clogging was measured, and immediately beforethe clogging, the operation was paused. The upstream filter was replacedby fresh one, and the operation was resumed. The result is shown in FIG.9. The filtration was conducted with three replacements and four8-minutes operations, and the total amount of filtrate was 3.5 times asmuch as the amount when only one filter is used. When the conventionaldisposable filter element is used and filtration is operated four times,four filter elements are required, i.e. the amount to be filtered willbe four times as much as the amount with one filter. Therefore, when thes filtration is conducted four times, the filter element of the presentinvention can attain approximately 87 % of the amount of filtrate usingthe conventional filter element (3.5 times/4 times), though with respectto the number of downstream filters, only 25% of the conventional filteris required (1 downstream filter/4 filter elements). Especially in thecase of the downstream filter in which an expensive fine membrane isused as a filter body, the present invention is effective.

In addition, the present invention is advantageous in that, by preparingvarious kinds of upstream filters 34 and downstream filters 36 andcombining those, various filter element can be obtained depending on thepurpose.

Various modifications can be made in the scope of the present invention.

In the embodiment of the present invention, the upstream filter 34 isplaced outside the downstream filter 36. However, modification can bemade by properly changing the flow route and the downstream filter maybe placed outside the upstream filter.

In the embodiment of the present invention, an O-ring is provided on theoutlet 60 of the downstream filter 36, for fixing the downstream filterto the housing. However, the downstream filter can be connected usingonly the O-ring. In this case, it is simply a tight-fit. Depending onthe situation, the downstream filter can be integrally formed with thehousing. In this case, the downstream filter is disposable.

Further in the embodiment, the upstream filter is loosely connected withthe downstream filter, and bypassing to the downstream filter may occur,though the amount is small. To block the bypass, a disk-shape cap can beused to seal the bottom end of the upstream filter 34, instead of theannular cap 42, or O-rings can be placed around the caps 42 and 44 asmentioned above, so that the spaces between the caps 42 and 50, andbetween the caps 44 and 52 are sealingly closed.

In an another modified embodiment, a group consisting of plurality ofthe upstream filter and a group consisting of plurality of thedownstream filter are prepared, and a combination of the upstream filterand the downstream filter can be properly selected depending on thepurpose. Both filters can be fixed to the same sealing cap. In thiscase, the upstream filter cannot be replaced, thus it is disposabletype. However, a combination of the upstream filter and the downstreamfilter composing the filter element of the present invention is properlyselected depending on the purpose, which provides advantages in thatvarious kinds of filter device having designated purpose can be attainedeffectively.

By using the filter element and the filter device having theabove-mentioned features, long-term usage of the downstream filterbecomes possible, which has been impossible with one conventionalhousing. In addition, a group of the upstream filter and a group of thedownstream filter is prepared and, two filters each selected fromdifferent group are used in combination. As a result, a user or aninstaller of the filter can properly select the filter combination andthe filter can be replaced at any time.

It is also possible to render additional property to an upstream filter,such as ion removing ability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a partial cross-section of a filter device having aconventional filter element.

FIG. 2 shows a specific phase diagram showing a conventional filterdevice having a conventional filter element.

FIG. 3 shows a longitudinal section of a filter device into which afilter element of the present invention is fixed.

FIG. 4 shows a perspective view of the upstream filter that is acomponent of the filter element of the present invention.

FIG. 5 shows a perspective view of the downstream filter that is acomponent of the filter element of the present invention.

FIG. 6 shows a perspective view of one embodiment of the presentinvention in which the filter elements are combined.

FIG. 7 shows a plane cross section along the line IV-IV in FIG. 3.

FIG. 8 shows a perspective view of the cross section of the filterelement along the line VIII-VIII in FIG. 3.

FIG. 9 shows a graph showing relationships between the flow time of thefeed and the total quantity of the filtrate in the case of the filterdevice of the present invention.

DESCRIPTION FOR NUMERALS

-   30 filter element-   32 filter device-   34 upstream filter-   36 downstream filter-   38 filter body-   40 housing-   42, 44 cap-   46 projection-   48 filter body-   50, 52 cap-   54, 62 support cylinder-   56 circulatory hole-   60 outlet-   58 twist-lock groove-   64 grommet groove

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 12. A disposable filter device having an upstream filter anda downstream filter integrally fixed in a housing, wherein each of saidupstream filter and downstream filter is selected respectively fromdifferent sets of filters.